Golden Eagle (Aquila chrysaetos)

This large and powerful raptor is an apex predator and a potent symbol of wildness, particularly in the north west Highlands.

 

Click on an image below to view the gallery.

Adult female golden eagle in flight. Photo by Laurie Campbell.
Juvenile golden eagle in a Scots pine tree. Photo by Laurie Campbell.
Mature female golden eagle scavenging at a red deer carcass in winter. Photo by Laurie Campbell.
Female golden eagle, with a chick in the nest. Photo by Laurie Campbell.

Worldwide distribution

The golden eagle is the most widely distributed eagle in the world, with a range that includes much of the world’s northern hemisphere. In North America, it occurs across most of Canada and Alaska and in the western USA and parts of Mexico. In Europe and Asia, it is found from Scotland across Scandinavia, the Baltic states and Russia to Siberia, Korea and Japan. Further south, it occurs in the Pyrenees, Alps, Carpathian and Caucasus Mountains, as well as in mountainous parts of Spain, Greece, Turkey, Iran, Afghanistan and eastwards to China. In North Africa its range includes Mauritania, Morocco, Algeria and Tunisia, and it also occurs in the Middle East, in Israel, northern Yemen and Oman, and in the Bale Mountains of Ethiopia. In general the golden eagle prefers open or semi-open areas, and does not occur in heavily-forested landscapes or areas with a dense human population, such as most of England or Germany. 

Six subspecies of the golden eagle are recognised, based on variations in size and plumage characteristics, and determined largely by geographic location.

Distribution in Scotland

In Scotland, the golden eagle occurs primarily north of the Central Belt, on the mainland and on the Hebridean islands. The population consists of over 400 pairs, with the greatest concentration occurring in the west of the mainland and on larger islands such as Mull and Skye. In the central and eastern Highlands the population is lower, and many areas of suitable habitat that were historically occupied currently do not have eagles in them. This is thought to be due primarily to ongoing illegal persecution, with fledged young eagles not surviving long enough to take up unoccupied territories and breed themselves.

There is a small population in the Southern Uplands, consisting of two to five pairs, although research has shown the region could support up to 14 pairs. 

Because of its very large geographic range and overall stable population, the golden eagle is classified as Least Concern on the IUCN Red List of Threatened Species, meaning that it is not facing any imminent threats at a global level. However, it is listed as a Category 3 Species of European Conservation Concern, meaning that it has an unfavourable conservation status in Europe. It is also listed on Annex 1 of the European Union’s Birds Directive, under which member states are required to designate Special Protection Areas (SPAs) for the listed species. In the UK, 14 SPAs have been established which benefit the golden eagle, including one stretching from Glen Affric to Strathconon. Further protection is provided in the UK by the eagle’s inclusion on Schedule 1 of the Wildlife and Countryside Act, under which it is an offence to damage or interfere with its nests or to harass birds. The golden eagle is also included on the Scottish Biodiversity List as a priority species for conservation.

Breeding begins when birds reach four or five years old, and have achieved full adult plumage. Courtship can include a pair flying together, and chasing or playful attacks on each other. Pairs usually stay together for life. Both the male and female take part in nest building, which is mostly done on cliffs but also sometimes on trees. An established pair will have several nests to choose from within their territory.

Two eggs are normally laid between early March and mid April, and incubation, mostly by the female, takes up to 45 days. The chicks hatch in May or early June and spend about 70 days in the nest before fledging in late summer. Often the first chick to hatch will kill its younger sibling. The adult male provides most of the food, and for the first few weeks after fledging the chicks will remain near the nest and continue to be fed by the adults.

In the wild the golden eagle has been recorded as living for up to 32 years, while in captivity individuals have reached 46 years of age. In Scotland, it is a sedentary species, meaning that it remains in its territory throughout the year, and does not migrate for the winter.

The golden eagle is a member of the Accipitridae family, which includes hawks, kites and harriers, as well as eagles. It is the second largest raptor in the UK, after the white-tailed or sea eagle (Haliaeetus albicilla). An adult has a body length of 80 – 93 cm. and a wingspan of 1.9 – 2.3 metres. Females are larger than males, and weigh from 3.7 – 6.5 kg., whereas the males range from 2.8 – 4.5 kg.

The plumage is mainly dark brown in colour, with a paler, golden area at the back of the head, which gives the species its common name. Immature or subadult birds are a deeper, more chocolate brown colour, with white patches on the tail and the undersides of the wings. The bare, un-feathered sections of the eagle’s feet are yellow, and the four talons on each foot are dark, curved and very sharp. Three talons point forwards, whilst the fourth and largest, the hallux talon, points backwards and is up to 6.3 cm. long.

The eyes are golden brown and the highly-curved bill is dark at the tip, fading to a lighter colour where it meets the cere, the yellow waxy area that contains the eagle’s nares, or nostrils.

In flight, the golden eagle spends most of its time soaring and gliding, utilising air currents and thermals, with relatively little time actually flapping its wings. When hunting it is capable of gliding at speeds up to 120 mph, and then diving at over 150 mph to seize prey in its talons. Most prey is killed on the ground by the powerful force exerted by the eagle’s talons.

In Scotland the prey varies depending on the location, with red grouse (Lagopus lagopus scoticus) and ptarmigan (Lagopus muta) being important food in the eastern Highlands, whereas mountain hares (Lepus timidus) are commonly caught on western islands such as Mull. Other prey species include black grouse (Tetrao tetrix), rabbit (Oryctolagus cuniculus), fox (Vulpes vulpes), roe deer calves (Capreolus capreolus) and smaller raptors such as the kestrel (Falco tinnunculus) and common buzzard (Buteo buteo).

The golden eagle feeds both by catching live prey and scavenging on carcasses of animals that have died from natural causes. The latter is particularly important in winter, with carrion from red deer (Cervus elaphus) and sheep (Ovis aries) probably providing its main food then.

Where their ranges overlap, the golden eagle will compete with the white-tailed or sea eagle for access to carrion. Although it is smaller, the golden eagle is strongly dominant in these situations. Where it is perceived as a threat, eg to their nests, smaller raptors such as the buzzard or crows (Corvus spp.) will engage in mobbing behaviour, to drive an eagle away.

Like most birds, the golden eagle is host to various external or ectoparasites. These include a feather mite (Pseudalloptinus aquilinus) and a skin-dwelling mite (Harpyrhynchus sp.), and two species of lice, one of which (Craspedorhynchus platystomus) lives on the head and neck, and the other (Falcolipeurus suturalis) occurs amongst the wing feathers. A large bird flea (Ceratophyllus vagabundus) has been found on fledglings and golden eagle nests in Alaska and Spitsbergen in Norway. Other fleas that are parasites on the eagle’s rodent prey are transported to the nest when their hosts are caught. The prevalence of ectoparasites such as these is thought to be the reason for the use by golden eagles of green plant material in their nests, as the foliage may contain aromatic compounds that repel the parasites.

As an apex predator, the adult golden eagle does not have any predators itself. In North America both the wolverine (Gulo gulo) and grizzly bear (Ursus arctos) have been recorded as taking unfledged birds from the nest. However, adults continue to suffer illegal persecution by humans in Scotland through poisoning, shooting and trapping, particularly in areas where land is managed for grouse moors, and this is the main factor limiting the eagle’s further re-colonisation of its former territories.

Alan Watson Featherstone

 

Sources and further reading:

 

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